The Department of Public Health and Environment proposed to amend 5 Colo. Code Regs. §1001-13, pertaining to the motor vehicle emissions inspection program. Changes would add nitrogen oxides tailpipe emission limits to the selection criteria used in the Clean Screen Program. The Department of Public Health and Environment proposed to amend 5 Colo. Code Regs. §1001-13, pertaining to the motor vehicle emissions inspection program. Changes would add nitrogen oxides tailpipe emission limits to the selection criteria used in the Clean Screen Program..